Information processing system and method

Abstract

An information processing system and method are disclosed in which information processing is performed in a highly efficient manner using an enabling key block (EKB) on the basis of a tree structure including category subtrees. A key tree is produced so as to include a plurality of subtrees that are grouped in accordance with categories and managed by category entities. An EKB is produced so as to include data produced by selecting a path in the key tree and encrypting an upper-level key in the selected path using a lower-level key in the selected path. The resultant EKB is provided to a device. If a change occurs in state of a category tree capable of processing an EKB identified in the EKB type definition list, a notification of the change in state is sent to an entity that uses the EKB thereby making it possible for an EKB requester to perform processing in accordance with a newest EKB.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to an information processing system, an information processing method, and an information storage medium, and particularly to a data distribution system and method for providing various kinds of data such as content data to an authorized user by means of a process including a cryptographic process. More particularly, the present invention relates to an information processing system, an information processing method, and an information storage medium, in which a key block is produced using a hierarchical-tree key distribution technique depending on a device to which content is to be provided, and the key block is used in encryption of the content and also in transmission of a content key, thereby ensuring that the content, the content key, and other data are securely provided.[0002]It is now very popular to distribute various kinds of software data such as a game program, audio data, and image data (hereinafter, such data...

AI Technical Summary

Benefits of technology

[0013]It is an object of the present invention to provide a technique of securely transmitting data only to authorized users without having to perform mutual authentication between a sender and a receiver, by using an encrypted key block which can be used (decrypted) in a plurality of category trees defined as subtrees in a hierarchical key distribution tree.

[0014]More specifically, it is an object of the present invention to provide an information processing system, an information processing method, and an information storage medium, in which an enabling key block (EKB) including encrypted key data which can be decrypted by one or more selected category trees is produced thereby making it possible for devices belonging to any one of the selected category trees to use the enabling key block (EKB), and an EKB type definition list, indicating which EKB type can be processed or decrypted by which category tree, is used thereby making it possible to perform production and management of enabling key blocks (EKB's) in a highly efficient manner.

[0015]It is another object of the present invention to provide an information processing system, an information processing method, and an information storage medium, in which a notification of a change in state of a category tree capable of processing an EKB identified in an EKB type definition list is sent to an entity that uses the EKB thereby making it possible to use newest EKB type definition information in processing.

[0039]Furthermore, the data size of the enabling key block is reduced by employing a data format including an encrypted key data part and a tag part indicating the locations of encrypted keys, thereby making it possible to perform decryption easily and quickly. That is, data is produced in an encrypted form that can be decrypted only by an authorized device whereby the data is securely provided to the authorized device.

[0040]Furthermore, an enabling key block (EKB) is produced so as to include encrypted key data that can be decrypted in selected one or more category trees thereby making it possible for any device belonging to any one of those selected category trees to use the enabling key block (EKB). The EKB is produced and managed in a highly efficient manner by using the EKB type definition list representing which EKB can be processed or decrypted in which category tree.

[0042]The program storage medium defines a cooperative relationship in structure or function, for realizing a function of a particular computer program on a computer system, between the computer program and the storage medium. That is, by installing a particular computer program onto a computer system via a program storage medium, it becomes possible to achieve a cooperative operation on the computer system thereby achieving functions similar to those achieved by the other aspects of the present invention.

Problems solved by technology

The common key is given only to authorized users so that unauthorized users who do not have the common key cannot access the data.

Although an encryption / decryption key can be generated using an output obtained by applying a unidirectional function to, for example, a password determined by a user, it is substantially impossible to determine, from the obtained encryption / decryption key, the password that is original data from which the encryption / decryption key is generated.

This results in inconvenience in renewal.

On the other hand, in the case where the public key encryptography is employed, undesirably complex calculations using a memory with an undesirably high capacity are required.

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